The invention relates to a scraping device for a rotary press comprising at least one scraping element for scraping pellets located on a die plate of the rotary press to an outlet.
Furthermore, the invention relates to a rotary press comprising a control device and a rotor that can normally rotate about a vertical axis, wherein the rotor has an upper and lower punch guide for lower and upper press punches and a die plate between the punch guides, wherein the press punches interact with openings in the die plate, furthermore comprising at least one filling and dosing station in which the material to be pressed is added to the openings, furthermore comprising at least one pressing station that, during operation, interacts with the upper press punches and the lower press punches such that they press the material located in the openings into pellets, and comprising at least one ejector station in which the pellets are conveyed out of the openings onto the die plate.
The invention relates to a method for operating a rotary press in which material added to holes of a die plate is pressed by upper and lower punches into pellets, the pellets are then conveyed onto the die plate and scraped off the die plate by a scraping element to an outlet.
An example of a rotary press is disclosed in DE 10 2007 057 791 B4. In addition to at least one filling and dosing station in which the material to be pressed is added to openings in the die plate, and a pressing station in which the material added to the openings is pressed by means of upper and lower press punches into pellets, especially tablets, such rotary presses also comprise in particular an ejector station. In the ejector station, the produced tablets are normally conveyed to the top side of the die plate by raising the lower punch. A stationary scraping element downstream in the direction of rotation of the rotor scrapes the tablets located on the rotating die plate off of the die plate, and conveys them into an outlet that for example leads to a discharge channel. Such scraping elements generally also comprise a sorting nozzle that sorts out tablets to be sorted out due to poor quality by means of directed compressed air into a reject channel.
Generally, pellets of different sizes are produced with such rotary presses. The scraping elements frequently comprise a crescent along which the pellets are guided to the outlet under the effect of the die plate which continues to advance by rotation under the stationary scraping elements. Depending on the size of the tablets, especially their diameter or another characteristic dimension if the shape is not circular, the scraping elements are individually positioned in order to ensure proper guidance by the scraping elements. This is generally done manually by an operator. Normally, the scraping element is pushed by the operator in a radial direction across the die plate in order to adapt it to the different tablet diameters or dimensions.
This known procedure is associated with several problems. On the one hand, repositioning the scraping element can change the angle between the sorting nozzle and tablets. The danger is then that bad tablets are no longer guaranteed to be properly sorted out by the sorting nozzle. In addition, given the frequently smooth adjustability of the scraping element, there is no guarantee that the scraping element will be correctly positioned by the operator for the respective tablet size. This can subject the tablets to significant stress while scraping. It can cause the tablets to become damaged or even break. Since bad tablets are normally rejected in the direction in which the tablets are conveyed before the actual scraping process, tablets that are damaged or broken during the scraping process cannot be sorted out. In certain circumstances, bad tablets are therefore fed to the tablet outlet for acceptable tablets.
Based on the explained prior art, the objective of the invention is to provide a scraping device, a rotary press and a method of the aforementioned type by means of which pellets are kept from being damaged by the scraping element, and bad tablets are guaranteed to be reliably sorted out.